1. Field of the Invention
This invention relates to a high resolution X-ray imaging apparatus for combining an optical image from a video system with a fluoroscopic image from an X-ray system.
2. Description of the Related Art
It is known that X-ray inspection techniques are used for quality control in the production of electronic components, such as integrated circuits, multi-layer printed circuit boards and surface mounted components. Conventional X-ray inspection systems produce an X-ray image of the object being inspected. In addition, X-ray inspection systems are used for producing images of patients during medical treatments.
U.S. Pat. No. 4,995,068 describes a radiation therapy imager for providing X-ray images of a patient while being treated on a radiation therapy machine for the purpose of verification and monitoring of the position of the patient. A fluoroscopic plate produces a fluoroscopic image of the patient. The fluoroscopic plate has a detection resolution of 1.6 lp/mm. A first remote camera picks up the fluoroscopic image. An image of a simulator radiograph is picked up by a second remote camera. A remote console has the capability of receiving input from both the first and second cameras and for aligning the fluoroscopic image with the radiograph film image. The technology described in U.S. Pat. No. 4,995,068 has the shortcoming that the observer is viewing two different objects from two different locations. Also, the resolution of the images from a fluoroscopic plate is inadequate for electronic component inspection.
U.S. Pat. Nos. 4,890,313 and 5,127,032 describe X-ray imaging systems for indicating alignment of X-ray beams with patient areas to be inspected. X-rays are projected at a 90.degree. angle to each other. A fluorescence screen is excited to emit light after receiving the X-rays. A thin deflection mirror is used to locate a video camera out of the path of the X-rays but in position to receive and record X-ray images on the fluorescence screen.
U.S. Pat. Nos. 4,974,249 and 5,113,425 issued to the inventor of this disclosure describe an X-ray inspection system for producing both film and fluoroscopic images of electronic components and assemblies therefor. An X-ray cabinet includes an X-ray tube and a slidable drawer for supporting the object to be inspected and film. An aperture is formed in the drawer to the X-ray tube. A fluoroscopic imaging device attaches to the slidable drawer for converting an X-ray image of the object to a fluoroscopic X-ray image. An output of the fluoroscopic imaging device is optically coupled to a video monitor. The fluoroscopic imaging device includes a thinly coated radioluminescent phosphor plate optically coupled to the input of an image intensifier. A microchannel plate image intensifier is used for providing a relatively high resolution image of the object.
Japanese Patent No. 54158984 describes an X-ray fluoroscopic inspection apparatus. X-rays are transmitted through a mirror. A camera picks up the transmitted X-rays after they pass through the object to be inspected. Visible rays from the object to be inspected reflect off the mirror and are picked up by an IVT camera. This patent has the drawback of scattering the X-rays with the mirror, thereby making the system unsuitable for detecting flaws in electronic components.
Conventional mirrors are formed of silica (glass) and oxygen. Silica has an atomic number of 14. When silica is used in the path of an X-ray beam, the silica absorbs the X-rays and re-emits secondary X-rays which effect is referred to in the prior art as scattering or Compton scattering. Scattering has the effect of formation of image noise which degrades the X-ray or fluoroscopic image. The degradation of the X-ray image is disadvantageous for high resolution inspection systems which congruently combine an optical image and an X-ray image of an object to be inspected.
Of possible general relevance are: U.S. Pat. Nos. 4,894,855, 5,038,369, and 5,119,409 directed to X-ray imaging systems.
For certain applications, such as inspection of electronic components, it is often desirable to optically view the object. In addition to X-ray inspection of the object, optical inspection can be used for determining various defects in the electronic components. An inspection system which combines an optical image from a video system with an X-ray image from an X-ray system in which both images are generated at the same location of an object to be inspected is not believed to be found in the prior art. It is desirable to provide a high resolution inspection system which congruently combines optical images and X-ray images of an object to be inspected.